In order to realize a high-speed and highly-integrated semiconductor device, demanded is a gate insulating film having a higher dielectric constant than that of SiO2 without leakage current problem. Candidate materials of such a gate insulating film are required to have some characteristics, such as not only a high dielectric constant, but also reactivity with Si, a level of band gap and the like. For example, HfO2 and HfSiOx are exemplified as materials that satisfy the above characteristics. Researches on such materials have recently been proceeding (see, for example, Patent Document 1, Non-patent Document 1).
Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2004-79606.
Non-patent Document 1: J. Appl. Phys. 89, pp. 5243-5275 (2001).